[Consequences for clinical biochemists of the modifications of the creatinine-based evaluation of glomerular filtration rate between 2005 and 2008]. / Evolution des modalités d'évaluation de la fonction rénale basée sur la créatinine entre 2005 et 2008: conséquences pour les biologistes.

Since 2005, international guidelines propose a stadification for chronic renal failure based on the glomerular filtration rate (GFR) value. The performance of the creatinine-based equations allowing the estimation of GFR and the bias of the creatinine measurements is, more than ever, a crucial issue. The consequences for the clinical biologists are of importance. First, the Cockcroft-Gault formula must be replaced by the four variable-MDRD equation. Second, the biologists must chose from the "175" and the "186" versions of the MDRD equation. The first one fits the creatinine methods which are traceable to the reference method (liquid or gas chromatography coupled to mass spectrometry). The second equation must be used for creatinine methods, which are not traceable to the reference method. Today, only some enzymatic methods can prove that they are traceable to the reference method. For the colorimetric methods, future is inclear.

[Evaluation of renal function: an update]. / Evaluation de la fonction rénale: une actualisation.

During the last years, GFR estimation has received substantial attention with a focus on comparing results of new formulas with GFR measurements, and standardization of creatinine assays. Calibration of creatinine should improve performances. However, frequently used equations have lower precision in high GFR populations. This is the reason why a continuous effort in improving predicting equations is still needed. The use of calibrated creatinine, the onset of new GFR markers such as cystatin C, and pooling data across many study populations are underway to develop better prediction.

[Cystatin C: current step and future prospects]. / Cystatine C: point d'étape et perspectives.

Cystatin C is a low molecular weight-protein, which may replace creatinine for the evaluation of renal function, particularly in the clinical settings where the relationship between creatinine production and muscular mass impairs the clinical performance of creatinine. This paper intends to summarize the current knowledge about the physiology of cystatin C and about its use as a renal marker, alone or within formulas developed to estimate the glomerular filtration rate. Moreover, this paper reviews the recent data about potential other applications of cystatin C, especially in cardiology, in oncology and in clinical pharmacology.

Zoledronic acid treatment impairs protein geranyl-geranylation for biological effects in prostatic cells.

BACKGROUND: Nitrogen-containing bisphosphonates (N-BPs) have been designed to inhibit osteoclast-mediated bone resorption. However, it is now accepted that part of their anti-tumor activities is related to interference with the mevalonate pathway. METHODS: We investigated the effects of zoledronic acid (ZOL), on cell proliferation and protein isoprenylation in two tumoral (LnCAP, PC-3,), and one normal established (PNT1-A) prostatic cell line. To assess if inhibition of geranyl-geranylation by ZOL impairs the biological activity of RhoA GTPase, we studied the LPA-induced formation of stress fibers. The inhibitory effect of ZOL on geranyl geranyl transferase I was checked biochemically. Activity of ZOL on cholesterol biosynthesis was determined by measuring the incorporation of 14C mevalonate in cholesterol. RESULTS: ZOL induced dose-dependent inhibition of proliferation of all the three cell lines although it appeared more efficient on the untransformed PNT1A. Whatever the cell line, 20 microM ZOL-induced inhibition was reversed by geranyl-geraniol (GGOH) but neither by farnesol nor mevalonate. After 48 hours treatment of cells with 20 microM ZOL, geranyl-geranylation of Rap1A was abolished whereas farnesylation of HDJ-2 was unaffected. Inhibition of Rap1A geranyl-geranylation by ZOL was rescued by GGOH and not by FOH. Indeed, as observed with treatment by a geranyl-geranyl transferase inhibitor, treatment of PNT1-A cells with 20 microM ZOL prevented the LPA-induced formation of stress fibers. We checked that in vitro ZOL did not inhibit geranyl-geranyl-transferase I. ZOL strongly inhibited cholesterol biosynthesis up to 24 hours but at 48 hours 90% of this biosynthesis was rescued. CONCLUSION: Although zoledronic acid is currently the most efficient bisphosphonate in metastatic prostate cancer management, its mechanism of action in prostatic cells remains unclear. We suggest in this work that although in first intention ZOL inhibits FPPsynthase its main biological actitivity is directed against protein Geranylgeranylation.

[Improving the interlaboratory variation for creatinine serum assay]. / Dosage de la créatininémie en 20003: état des lieux analytique et essai de standardisation de l'étalonnage.

PURPOSE: To assess inter-assay variation and accuracy of blood creatinine measurements as well as the effect of the standardization of the calibration procedures on inter-assay variation. METHODS: Inter-assay variation and accuracy were assessed using 30 frozen human sera and 3 certified reference materials, which were analysed by 17 creatinine assays (colorimetric: 12, enzymatic: 4, HPLC: 1). Usual calibration procedure was compared with two common calibration procedures using either a reference material (404.1 micromol/L), or secondary sera calibrators (69, 115 et 180 micromol/L). RESULTS: Most of the commercially available methods display inaccuracy, > 10% for creatininemia < 150 micromol/L in most cases. For this concentration range, the mean creatininemia was statistically significantly different as a function of the assay used (p < 0.001). Enzymatic assays produced lower results than colorimetric ones for low creatinine levels but higher results for high creatinine levels. Assays being calibrated according to the manufacturer's recommendations, the median dispersion factor was 14% for the 20 samples between 45 and 150 micromol/L, and 8% for the 10 samples between 250 and 350 micromol/L. The calibration procedure modified inter-assay variation significantly (p < 0.001) but we gained little advantage from both common calibration procedures. A significant decrease of inter-assay variation occurred within each technical group (colorimetric or enzymatic) when a common calibration was performed using calibrators which concentration(s) was(were) close to the concentrations to be measured. CONCLUSIONS: Inter-assay variation is too high to allow prediction of glomerular filtration rate (GFR) or creatinine clearance from serum creatinine level. Our results highlight the interest of a calibration procedure using several concentrations with at least one between 90 and 150 micromol/L. The marketing of such a calibrator should be considered in order to decrease inter-assay variation in the range of creatinine levels which defines a mild chronic renal failure. Such an approach will certainly reduce inter-assay variation only within each technical group but could allow to include technical group as a co-variable in the algorithms developed for predicting GFR or creatinine clearance. A global transferability will certainly need the correlation of all types of creatinine assays versus a definitive method, whom definition remains uncertain.

Impact of the biochemical assay for serum creatinine measurement on the individual carboplatin dosing: a prospective study.

We previously developed a formula to estimate the individual carboplatin clearance (CL) based on serum creatinine (Scr) determined by an enzymatic assay using creatinine amidohydrolase. An analytical comparison had shown systematic differences between this method and the commonly used Jaffé method (with Jaffé Scr (in microM)=1.08 x enzymatic Scr+1.6, as regression equation). We performed a pharmacokinetic prospective clinical study using the Jaffé assay to evaluate the impact of the method used for Scr measurement on the prediction of the carboplatin CL. In forty patients, carboplatin dosing was performed according to the Chatelut formula where the serum creatinine level was corrected according to the above equation. The population pharmacokinetics of carboplatin were analysed using the NONMEM program to determine the individual carboplatin CL from a limited sampling strategy. Thanks to the correction of the Jaffé Scr, no significant difference was observed between the administered and the optimal dose. In contrast, if no correction of the Scr was done, the patients would have been significantly under-dosed. Moreover, a covariate analysis using NONMEM gave a very consistent result showing that Scr should be decreased by 11.6% when the Jaffé value is used within the Chatelut equation. This study confirmed that differences in the Scr assay has consequences with regard to carboplatin dosing. The correction we propose for Scr obtained by the Jaffé method may help to standardise clinical practice.

Carcinocythemia as the single extension of breast cancer: report of a case and review of the literature.

Carcinocythemia (carcinoma cell leukemia) has been previously described as a rare, late and dramatic event occurring in widespread tumoral disease. We report a case of carcinocythemia occurring in a patient with a particularly indolent breast cancer. When a large amount of circulating tumor cells (CTC) appeared in the blood smears, neither visceral macrometastases nor massive bone marrow infiltration could be detected. We isolated CTC to perform cell cycle analysis and to study the expression of adhesion molecules. A fraction of the CTC was proliferating in the bloodstream but we detected no relevant anomaly of adhesion properties in the CTC. A post-mortem biopsy disclosed an exclusive sinusoidal infiltration of the liver. We propose that in this case, carcinocythemia resulted from the release of CTC from the visceral microcirculation where the proliferation occurred.

Reversion of transformed phenotype of human adenocarcinoma A549 cells by expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase complementary DNA.

3-Hydroxy-3-methylglutaryl CoA reductase (HMG-CoA reductase) plays a rate-limiting role in isoprenoid biosynthesis and is associated with cell proliferation and transformation. Although an elevated level of HMG-CoA reductase activity is consistently detected in cancer cell lines and tumors, the question remains whether HMG-CoA reductase activity may have a causative role in cell transformation. We have stably transfected the A549 human adenocarcinoma cells with both bicistronic and retroviral expression vectors, including the whole cDNA of human HMG-CoA reductase. Stably transfected cells showed strong morphological changes and disorganization in the filamentous actin architecture, became contact inhibited, and had a lower doubling time. Moreover, they exhibited anchorage-independent growth reduction and lost their capability to induce tumors in nude mice. Surprisingly, no quantitative modification of enzyme activity was observed following transfection, although expression of HMG-CoA reductase cDNA was shown by Northern blot analysis. When endogenous and transfected reductase activity was bypassed by the addition of mevalonate and compactin, a competitive inhibitor, the filamentous actin distribution in HMG-CoA reductase-transfected cells became very similar to that of control cells, demonstrating the role of exogenous HMG-CoA reductase activity in this process. All of our data together strongly suggest that phenotype reversion is dependent on exogenous HMG-CoA reductase expression and that enzymatic activity is implied in this mechanism. HMG-CoA reductase cDNA expression, by expression of a particular form of reductase, might be a negative regulator of cell growth and thus reverse the phenotype of tumor cells.